1. An "open bubbling culture system" was devised for the mass-culture of a blue-green alga,
Tolypothrix tenuis, with the special purpose of using the organism as a new green-manure in the paddy fields of this country.
2. To minimize the cost of production, the utilization of natural resources was intended, using hot spring water and natural gas (methane) as the heat and carbon dioxide sources. The heat of combustion of the natural gas (to make carbon dioxide) was also used in warming the culture.
3. The growth rate of the alga obtained with this culture equipment (250 1 culture volume, 5 square meter surface) amounted to 6.4g (dry weight) per square meter per day,
i.e., a yield of 7.0 tons of the alga per annum.
4. The prospect of practical application of the system was discussed on the basis of the experimental results obtained.
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